1. Field of the Invention
The present invention relates to a cuff for a sphygmomanometer, particularly to a sphygmomanometer cuff wrapped around the region of measurement such as the upper arm or wrist used to increase the pressure at that region to measure blood pressure.
2. Description of the Background Art
FIG. 6 is a perspective view of an entire sphygmomanometer cuff. Referring to FIG. 6, a sphygmomanometer cuff 70 includes an outer cuff piece 71, an inner cuff piece 72, a bladder 73 provided inside a band-like bladder formed of outer cuff piece 71 and inner cuff piece 72, and a clip plate 74 arranged outside bladder 73 to suppress the outward swell of bladder 73 and maintain a predetermined curved configuration in an elastic manner. Hook-and-loop fasteners 75 and 76 are provided at outer cuff piece 71 and inner cuff piece 72, respectively. Cuff 70 is fastened to the measurement region in a wrapped-around manner by hook-and-loop fasteners 75 and 76.
Such a cuff 70 is provided in a wrist sphygmomanometer as shown in FIG. 7, for example, and attached to a sphygmomanometer unit 80.
Bladder 73 used in the aforementioned cuff 70 includes an outer wall 61 and an inner wall 62, as shown in FIG. 4 (the upper portion corresponds to a deflated state and the lower portion corresponds to an inflated state). Walls 61 and 62 are fixed with each other by melting or the like at both ends 63 in the wrapping direction.
Inflation of bladder 73 results in a smaller width of bladder 73 (the dimension perpendicular to the wrapping direction). Pressure caused by inflation of bladder 73 may not be applied sufficiently to the artery located in the measurement region around which cuff 70 is wrapped to degrade the reliability of the blood pressure measurement precision. Particularly in the case of cuffs for wrist sphygmomanometers, there are many disadvantages in blocking the flow of blood since there are more tendons and the like at the wrist than at the upper arm. Therefore, the cuff for a wrist sphygmomanometer requires a higher performance of blocking blood flow than that of the cuff for the upper arm. It is difficult to apply sufficient pressure to the region where blood flow is to be blocked and the blood flow could not be blocked favorably if the conventional cuff configuration was used in which the width becomes smaller.
Japanese Patent No. 2840075 B2 discloses a cuff band for a wrist sphygmomanometer as schematically shown in FIG. 5 (the upper portion corresponds to a deflated state and the lower portion corresponds to an inflated state). Referring to FIG. 5, a blood blocking cuff (bladder) 50 is formed in a bladder configuration with two inner and outer cuff pieces 51 and 52 and side walls 53. Side wall 53 serving to inflate blood blocking cuff 50 in the thickness direction by the introduction of air into blood blocking cuff 50 is provided in a direction (the direction indicated by the arrow in FIG. 5) crossing the direction of inner cuff piece 52 wrapping around the wrist.
Since side walls 53 project outwards when air is introduced into blood blocking cuff 50, the width of blood blocking cuff 50 does not change although it is inflated. However, there is a problem that, after air is discharged, side walls 53 will not return to the original configuration of inward folded state.
In view of the foregoing, an object of the present invention is to provide a sphygmomanometer cuff that can maintain its former configuration in both the inflated and deflated state without change in the width even if the bladder is inflated and without expanding in the width direction when inflated.
To achieve the above object, the sphygmomanometer cuff of the present invention includes a bladder that inflates and deflates by the input and output of a fluid. The bladder includes an outer wall located at the outer side, an inner wall located at the inner side, a side wall connected to both ends in the wrapping direction of respective outer and inner walls, and folded inward in the bladder, and a joint coupling the side walls inside the bladder.
Since the bladder includes a joint that couples both side walls within the bladder in addition to the outer wall, inner wall and side walls in this cuff, the bladder maintains its configuration in which both side walls are folded when there is no fluid (water, air, or the like) in the bladder. Introduction of a fluid into the bladder causes the side walls to dilate outward from the folded state. However, since side walls are connected by the joint, the side walls do not project outwards, and the cuff is inflated in the direction of the thickness as the side walls extend substantially straight in the direction of the thickness of the cuff. Therefore, the bladder does not expand in the direction of the width when inflated. The width of the bladder hardly differs from that prior to inflation. When the fluid in the bladder is discharged, the side walls easily return to the folded state by virtue of the joint as the outer wall and the inner wall approximate each other and is eventually restored to the state prior to inflation.
By setting the side walls harder than the outer and inner walls in the above structure, the balance of weight of the bladder is improved particularly during inflation, so that pressure can be applied more stably at the measurement region with the cuff.
The details of setting both side walls harder than the outer wall and the inner wall will be described here. In the case where the side wall, the outer wall, and the inner wall are all to be formed of the same material, for example using a soft vinyl chloride sheet of the same type, the thickness of the side wall is set to 0.4 mm and the thickness of the outer wall and the inner wall is set to 0.2 mm, by way of example. Alternatively, when different materials are to be used, the type and thickness of each material is to be selected appropriately so that the side wall is harder than the outer wall and the inner wall.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.